Due to the no-Sound issue, which is STILL NOT SOLVED (see other thread) on WIn10, I installed Agressors Ancient Rome on my Win8.1 OS.

On first startup after install the game executable - or something - complains about missing DotNET runtime libraries. So, I installed them and on the next attempt to start the game it throws me a crash error message.

The same Windows 8.1 OS, which plays GTAV on max settings without any issues.

Thanks again, Pavel

I repeat what worked here, just in case somebody else is googlebinging for the question/solution. (Otherwise, somebody can delete this thread because of redundancy?)

1. Yes, having "Windows Media Player" installed (and working) solves the "no-sound" issue, completely.

2. My copy of the game repeatedly crashed on start on a freshly installed Win8.1 (with working GTAV on it), because
I never started the Windows Media Player!

Starting Windows Media Player at least ONCE, allowing it to manage all file types, and then closing it. Starting the game afterwards - all works as intended.